1. Field of the Invention
The present invention relates to the process of transferring data between integrated circuits. More specifically, the present invention relates to a sense amplifying latch with low swing feedback for amplifying capacitively coupled inter-chip communication signals.
2. Related Art
Advances in semiconductor technology presently make it possible to integrate large-scale systems, including hundreds of millions of transistors, into a single semiconductor chip. Integrating such large-scale systems onto a single semiconductor chip increases the speed at which such systems can operate because signals between system components do not have to cross chip boundaries and are not subject to lengthy chip-to-chip propagation delays. Moreover, integrating large-scale systems onto a single semiconductor chip significantly reduces production costs, because fewer semiconductor chips are required to perform a given computational task.
Unfortunately, these advances in semiconductor technology have not been matched by corresponding advances in inter-chip communication technology. Semiconductor chips are typically integrated onto a printed circuit board that contains multiple layers of signal lines for inter-chip communication. However, signal lines on a semiconductor chip are about 100 times more densely packed than signal lines on a printed circuit board. Consequently, only a tiny fraction of the signal lines on a semiconductor chip can be routed across the printed circuit board to other chips. This problem creates a bottleneck that continues to grow as semiconductor integration densities continue to increase.
Researchers have begun to investigate alternative techniques for communicating between semiconductor chips. One promising technique involves integrating arrays of capacitive transmitters and receivers onto semiconductor chips to facilitate inter-chip communication. If a first chip is situated face-to-face with a second chip so that transmitter pads on the first chip are capacitively coupled with receiver pads on the second chip, it becomes possible to transmit signals directly from the first chip to the second chip without having to route the signal through intervening signal lines within a printed circuit board.
However, it is not a simple matter to transmit and receive signals across capacitive pads. One problem is that signals become attenuated by the relatively large capacitance caused by layers of metal and silicon dioxide underneath the capacitive pads. In order to deal with this attenuation problem, the received signal needs to be amplified using a sensitive amplifier.
Unfortunately, increasing the sensitivity of the circuitry to small signals also increases the sensitivity of the circuit to noise. The reverse is also true. Reducing the sensitivity of the circuit to noise also reduces the sensitivity of the circuitry to small signals.
Hence, what is needed is a method and an apparatus for transmitting capacitively coupled signals between semiconductor chips without the problems described above.